linux-kernel - Re: [PATCH v2 1/2] 6lowpan: Make a copy of skb's delivered to 6lowpan

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Message-ID: <5040C283.7040809@signal11.us>
Date:	Fri, 31 Aug 2012 09:56:19 -0400
From:	Alan Ott <alan@...nal11.us>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Alexander Smirnov <alex.bluesman.smirnov@...il.com>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Tony Cheneau <tony.cheneau@...esiak.org>,
	linux-zigbee-devel@...ts.sourceforge.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] 6lowpan: Make a copy of skb's delivered to 6lowpan

On 08/31/2012 03:01 AM, Eric Dumazet wrote:
> On Wed, 2012-08-29 at 22:39 -0400, Alan Ott wrote:
>> Since lowpan_process_data() modifies the skb (by calling skb_pull()), we
>> need our own copy so that it doesn't affect the data received by other
>> protcols (in this case, af_ieee802154).
>>
>> Signed-off-by: Alan Ott <alan@...nal11.us>
>> ---
>>  net/ieee802154/6lowpan.c |    9 ++++++++-
>>  1 files changed, 8 insertions(+), 1 deletions(-)
>>
>> diff --git a/net/ieee802154/6lowpan.c b/net/ieee802154/6lowpan.c
>> index 6a09522..ce33b02 100644
>> --- a/net/ieee802154/6lowpan.c
>> +++ b/net/ieee802154/6lowpan.c
>> @@ -1133,6 +1133,8 @@ static int lowpan_validate(struct nlattr *tb[], struct nlattr *data[])
>>  static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
>>  	struct packet_type *pt, struct net_device *orig_dev)
>>  {
>> +	struct sk_buff *local_skb;
>> +
>>  	if (!netif_running(dev))
>>  		goto drop;
>>  
>> @@ -1144,7 +1146,12 @@ static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
>>  	case LOWPAN_DISPATCH_IPHC:	/* ipv6 datagram */
>>  	case LOWPAN_DISPATCH_FRAG1:	/* first fragment header */
>>  	case LOWPAN_DISPATCH_FRAGN:	/* next fragments headers */
>> -		lowpan_process_data(skb);
>> +		local_skb = skb_copy(skb, GFP_ATOMIC);
>> +		if (!local_skb)
>> +			goto drop;
>> +		lowpan_process_data(local_skb);
>> +
>> +		kfree_skb(skb);
>>  		break;
>>  	default:
>>  		break;
> Its not clear to me why skb_copy() is needed here.
>
> >From patch description, I would say skb_clone() would be enough (and
> faster) ?

You're probably right. I'll check it out. Thanks.

Alan.
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